MUST WATCH

Story highlights

Washington (CNN)More than 40 Afghan security force members training in the US have gone AWOL since last year, including eight last month, according to the US military.

One of those eight who vanished in September was detained by Canadian police while attempting to cross the US-Canada border, Cmdr. Patrick Evans told CNN Thursday.

A total of 45 members of Afghanistan's security forces have been reported absent without leave (AWOL) while in the US since the start of 2015. Of those, the whereabouts of 13 remain unknown, Evans said.

The Department of Homeland Security is responsible for tracking them down once they are reported missing, according to the military.

The 32 that have been located, Evans said, have either been deported, arrested and jailed, crossed an international border, or applied for immigration benefits.

The training is part of an international effort to boost Afghanistan's ability to defeat the Taliban and the AWOL students were undergoing instruction in a variety of topics, including leadership, language, infantry, aircrew, intelligence, engineering, military police, ordnance, transportation and Army Ranger training, US officials said.

A large number of Afghan soldiers and police have undergone training in the US since the international effort to build-up Afghanistan's security forces began. Since 2007, US facilities have hosted 2,207 Afghan trainees, the Department of Defense said in a statement.

"It is important to note that the majority -- well over 90% -- of Afghans who train in the US successfully complete their training and return to their country," Evans told CNN.

But Pentagon officials also said that the US is looking at ways to curtail these type of incidents. "DoD is assessing ways to strengthen eligibility criteria for training in ways that will reduce the likelihood of an individual Afghan willingly absconding from training in the US and going AWOL," Evans added.

US officials also stressed that there is currently a vetting process in place as part of the requirements of the "Leahy Law," which governs rules for the training of foreign military and security personnel.

The vetting is to insure the students have no links to terrorist or insurgent groups and have not committed any human rights violations. The trainees are also required to go through the regular US visa application process.

"If at any time they fail one of these steps, they are ineligible to go to this training or any future US-funded training," Defense Department spokesman Adam Stump told CNN.

Afghan security personnel are also screened for such ties by the Afghanistan government upon enlistment.

The eight trainees that went missing in September were not acting as a group when they vanished, Stump said.

The September uptick in disappearances could be related to the summer season in Afghanistan which tends to witness an increase in fighting as the Taliban typically launch their offensives during that time. One such attack brought Taliban fighters close to the center of the provincial capital city of Kunduz, a push that was recently beaten back by Afghan troops backed by airstrikes and US special operations forces.

But most experts believe the disappearances are likely more tied to economic concerns as many of the Afghan trainees have received extensive English language training and therefore think they would be better able to find work in the US or Canada.

Back in 2014 three trainees went AWOL from a facility in Massachusetts. The eight that absconded in September did so from military facilities in Fort Benning, Georgia, Fort Gordon, Georgia, Fort Lee, Virginia, Little Rock Air Force Base, Arkansas, Fort Leonard Wood, Missouri, and Monterey, California.